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  1. #1
    Just a bit of BOOST
    Join Date
    May 2017
    Location
    Newton Massachusetts
    Posts
    3

    Poor performance from my SVO

    Hey everyone, I just picked this '84 SVO last Sunday. It seems to have the mods to transform it into an 86 power wise. I was having an issue where the idle would raise itself while I was driving but I unplugged the IAC and believe that it is what was causing the issue as it went away. I did perform the base idle/TPS reset. Aside from that, the car has very sluggish performance. It will boost to what looks to be around 16psi, but it just doesn't feel fast. I believe I may have tracked down the issue, the injectors are green 36lb units and I tested the impedance and they were at 13. I have read that the SVO needs the low impedance injectors and with the PE computer I have I am going to get a set of browntop 35lb ones. Do you all think this could be the reason for my lack of power? I also received a lot of great advice on what to do on the a social media fan page. I am attaching pictures of the mods so if anyone could tell me what they see mod-wise it would be greatly appreciated. I am looking forward to being a part of this community! My previous car was a heavily modified 1984 Saab 900 Turbo which I loved to death but it was no longer practical to keep. I must say I'm very impressed with the handling of the SVO and love the exhaust note and noises! The car is also running much better then it was last week, I changed the plugs for the correct ones (it had the quad tipped platinum plugs in it).... which seemed to help out a lot!
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  2. #2
    OVER-BOOST!! gbeaird's Avatar
    Join Date
    Apr 2002
    Location
    Pearland, Texas
    Posts
    1,801
    SVO's: '86 2R
    And what did you gap those new plugs at? Since you're not new to the turbo world, I'm assuming you know they don't like a lot of gap? Otherwise, I'd start at a check of the running fuel pressure, then probably put a volt/ohm meter on the TPS and VAM to make sure they are working properly.
    Gene Beaird,
    86 2R SVO, G Stock,
    Pearland, Texas

  3. #3
    OVER-BOOST!! GAboySVO's Avatar
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    Dec 2002
    Location
    Acworth, GA
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    3,125
    SVO's: 2 - 9Ls
    I notice a couple of things:

    1. Is there an orange ground wire going from the BAP harness on the PS shock tower to the Compressor side of the turbo. If not, it can cause issues with the electronics.

    2. It is using an inline intake and a PE ECU, make sure the knock sensor is unplugged. The inline intake has a difference resonance than the square intake that is associated with the PE.

    Other things to do:

    1. Remove and clean the internals of the IAC and plug it back in.

    2. Verify the high idle wasn't caused by a flat spot in the TPS.

    3. If the plug wires are of unknown age, replace them with a set of Autolite or Motorcraft units.

    4. Verify your base fuel pressure and pressure rises under boost.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  4. #4
    Max BOOST! Chuck's Avatar
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    Aug 2003
    Location
    Sunny Phoenix, AZ
    Posts
    497
    SVO's: 1986 2A
    Welcome to the SVO world. If you thought a Saab was impractical to keep up, you've attained a new pinnacle of success with an SVO. You'll learn what I mean when you go to buy parts. You have to tell everyone the WHOLE name of your car...a 1984 Mustang SVO! If you don't, you get regular Mustang parts which probably will not work. The good news is your collection of tools will almost double since it is usually a guess on whether or not a bolt is SAE or Metric.
    <-Find the car; women: 0.001 secs, men: 2.4 mins.

  5. #5
    Max BOOST! High Roller's Avatar
    Join Date
    Apr 2002
    Location
    Tupelo, MS.
    Posts
    406
    SVO's: 84 9W, 85 1B
    This may sound crazy, but have you checked the catylytic converter? My 84 was very sluggish when I first got it. It turned out to be a clogged converter .Opened it up and it ran great.
    Perry Mitchell
    SVOCA#187

  6. #6
    Administrator SVOeric's Avatar
    Join Date
    Mar 2002
    Location
    Richmond, KY
    Posts
    12,497
    SVO's: 86-1C & 86-1E
    unplugging the IAC didn't fix your idle problem. it masked it by removing the component the computer uses to adjust the idle (for AC, idle when cold, etc)
    Idle issues are generally caused from TPS issues, flat spots, incorrect base setting (TPS is adjustable in these cars). There is a procedure for setting idle, should be in the FAQ section, but you have to follow the steps.

    Air leaks, can also cause idle issues. and the one a lot of people don't get, the crank-case is one of those places.

    and yes, you'll need to dump those high impedance injectors for it to run properly.
    Eric C
    SVOCA Webmaster

  7. #7
    Just a bit of BOOST
    Join Date
    May 2017
    Location
    Newton Massachusetts
    Posts
    3
    Thanks for all the responses. I decided to check the fuel pressure and saw it was set way to low. I raised the fuel pressure and that fixed the idle issue. I also replaced the injectors with some 35# browntops. Unfortunately, the car still broke up and ran poorly. I decided to make a boost leak tester and found that the car was leaking at the IAC gasket as well as out the FPR. I replaced the fpr with a stock one from autozone and here's where I am at now.

    While driving, fuel pressure at idle is from 28-29 psi. If I floor it, the pressure will immediately jump to 39-40psi but will not rise with boost. With the vac line off the fpr, it is steady at 40psi. Any idea what to do here? Replacing the fpr solved my backfiring/rough running issue. The car is smooth on acceleration now but just very slow. I am going to replace the fuel filter today and am going to try and DIY smoke test it by modifying a party store smoke machine to feed into the intake.

    I'm making progress slowly.

    Thanks!

  8. #8
    OVER-BOOST!! GAboySVO's Avatar
    Join Date
    Dec 2002
    Location
    Acworth, GA
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    3,125
    SVO's: 2 - 9Ls
    Based on what you are saying, the intake and thus the FPR port is not seeing any boost pressure. Does your boost gauge show any indication of boost building during acceleration? If not, then you wastegate flapper is being held open.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  9. #9
    Administrator SVOeric's Avatar
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    Mar 2002
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    Richmond, KY
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    12,497
    SVO's: 86-1C & 86-1E
    Quote Originally Posted by Beyondthesea View Post
    While driving, fuel pressure at idle is from 28-29 psi. If I floor it, the pressure will immediately jump to 39-40psi but will not rise with boost. .
    Thanks!
    IMHO -- this is your next hurdle.

    fuel pressure not being enough at boost will cause you to run lean, and can cause engine damage if not corrected.

    Make sure the dudes at auto-zone got you the right FPR, not a NA one.
    next is to replace the fuel filter.
    If those don't help, then you're looking at a fuel pump replacement. 84-85's have 2 pumps, low pressure in-tank, and high pressure
    typically the easier solution is to switch to the 86-up later style single in-tank pump



    next question are -- have you checked codes ??
    Eric C
    SVOCA Webmaster

  10. #10
    Just a bit of BOOST
    Join Date
    May 2017
    Location
    Newton Massachusetts
    Posts
    3
    Alrighty guys, thanks for the replies!

    1. The boost gauge does show pressure building.

    2. I haven't checked codes nor do I know how.

    Today's Update: I found out that someone had converted the car to a single pump configuration. Having read multiple writeups about this. I decided to check the black resistor wire that was there for the stock two pump configuration. Sure enough, it was not properly modified for the single pump. I cut and spliced regular wire in and grounded it in the trunk. That fixed my pressure issue and because I had put the adjustable FPR back in (I fixed its air leak), the car was getting 70-80psi at idle because I had it turned up so high. I turned it to 42 at idle and it will jump up to 55-60 at WOT, although I'm not sure the rise is linear with the boost increase. The car will rev out more now and is definitley much peppier but it is still not as fast as it should be.

    Now for the bad, the car was running fine until it started doing the hanging idle thing again after I had fixed the fuel pressure. Additionally, I found a vacuum leak at the throttle body shaft. I actually removed the throttle plate and shaft, used RTV around it to try to seal it but it did not work. Does this mean I need a new throttle body? The leak seems very significant. When using my DIY boost pressure tester hooked up directly to the TB, the system will bleed out all the air I pump in through the throttle body shaft. I'm assuming this is what is causing my new idle issue and the decreased performance I'm experiencing? I have some pictures and a video of this that I can upload later tonight/tomorrow.

    Thanks again for the help and I feel as if I'm getting closer to getting this thing running as fast as it should!

  11. #11
    OVER-BOOST!! GAboySVO's Avatar
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    Dec 2002
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    Acworth, GA
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    3,125
    SVO's: 2 - 9Ls
    The air leak around the TB shaft will definitely affect the idle and performance as it is letting in un-metered air. Under boost, you will have a pressure leak and the AFR will go to the rich side and reduce power. You may be able to ask the web for replacement seals. I never found them when I searched and upgraded to 70mm TB I won at the reunion. You may check over at turboford as well.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  12. #12
    Administrator SVOeric's Avatar
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    Mar 2002
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    Richmond, KY
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    12,497
    SVO's: 86-1C & 86-1E
    Quote Originally Posted by Beyondthesea View Post
    2. I haven't checked codes nor do I know how.
    all in the FAQ section, as well as TPS Setting procedure, which if not done correctly can also cause the 'hanging idle thing'
    Codes -- http://www.svoca.com/forum/showthrea...-and-code-list
    TPS ---- http://www.svoca.com/forum/showthrea...-and-Base-idle
    Eric C
    SVOCA Webmaster

  13. #13
    OVER-BOOST!! svono50's Avatar
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    Apr 2002
    Location
    Streamwood, IL
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    3,405
    SVO's: 86 1C
    Mike is correct, you are narrowing down your issues, good work! The leak at the TB shaft can cause issues on both sides of the equation as noted.

    Hmm, the TB shaft seals used to be available, but it has been a long, long time since I checked. I replaced mine back in the early/mid-90's so take that into account. I would think that a 'generic' shaft seal could be sourced, just need the ID of the housing recess and OD of the shaft, along with making sure it is rated for pressure and vacuum. May need to tap some of my industrial supply sources here at work to see if I can dig something up.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

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